This invention relates generally to wireless networks employing dynamic link adaptation algorithms with selectable coding schemes. In particular, the invention relates to a method for determining coding scheme adaptation capability of mobile stations within a General Packet Radio Service (GPRS) network or other mobile telephony system using memory for data packet transmissions.
With wireless networks employing General Packet Radio Service (GPRS), a mobile station may be directed by a base station to transmit data blocks using a coding scheme that the network determines will result in the highest data throughput with the fewest possible retransmissions. GPRS is an extension of circuit-switched networks and data transmission services that use packet radio transmissions to carry end user""s packet data using protocols such as Internet Protocol (IP) or X.25 information from mobiles to the network and visa versa. GPRS is an extension to the circuit-switched Global System for Mobile communications (GSM), having four different coding schemes with data rates of 9.05, 13.4, 15.6 and 21.4 kilobit per second (code rates xc2xd, ⅔, xc2xe and 1).
GPRS-enabled networks send commands to a mobile station, such as a cell phone, an Internet-enabled mobile phone or a personal digital assistant, to transmit data blocks at what it determines to be an optimal coding scheme. The selected coding scheme may rapidly degrade, however, with changing radio conditions or geographical movements of the mobile device. The mobile unit may have limitations in its coding capabilities and its ability to adapt to updated coding scheme commands. With the move toward third-generation network standards, there are even more possible problems with high-performance networks that use aggressive and dynamic coding schemes. Mobile stations need to adapt their coding schemes rapidly, and the networks need to recognize certain mobile stations that are unable to adapt quickly to avoid undue overhead in requesting code scheme changes that cannot be accommodated.
Problems between networks using aggressive coding schemes and certain mobile devices may occur when the mobile device is unable to respond to a coding scheme command. The mobile device may receive a request to change the coding scheme. During the allowed response time, the mobile station may send data blocks using the current coding scheme, giving the mobile station a chance to empty its buffers of uplink data that has already been segmented. Alternatively, during the response period, the mobile device may transmit a special control block to the network stating there is no data ready for transmission. This null data block may be referred to as a packet uplink dummy controlled block, or simply a packet uplink dummy.
Current dynamic link adaptation methods monitor the quality of packet transfers and changing channel-coding schemes based on changing radio conditions. These methods may have difficulty with mobile stations that send null data control blocks. The network may try to continue changing coding schemes as the null blocks are being sent, with the result that little end-user data is transferred and throughput is significantly reduced. Unfortunately, the more dynamic the link adaptation method is, the lower the throughput may be for an older or less provisioned mobile station. As technologies and protocols emerge and evolve for wireless data transmissions, additional coding schemes become available. For example, GSM networks incorporating Enhanced Data for Global Evolution (EDGE) with packet-switched enhancements for GPRS have nine additional coding schemes for increased performance. Other wireless network technologies such as GSM/EDGE Radio Access Network (GERAN) and Universal Mobile Telecommunications System (UMTS) provide enhanced coding schemes, requiring network algorithms that can determine the coding scheme adaptability of the mobile station and direct coding scheme commands to the mobile station based on the adaptability.
A desirable dynamic link adaptation method would be able to determine the coding capabilities of a mobile station and adapt its coding scheme to that device. The method would be able to detect, for example, when a mobile station is sending packet uplink dummies or null data blocks, and then use this information to determine future channel coding messages.
It is an object of this invention, therefore, to provide a method and system for determining coding scheme adaptation capability of wireless data devices, and to overcome the deficiencies and obstacles described above.
One aspect of the invention provides a method and system for determining coding scheme adaptation capability of a mobile station. A packet uplink acknowledgement is sent to the mobile station and a data packet including a coding scheme indicator is received. A determination is made on whether a coding scheme associated with the mobile station is adaptable and the coding scheme is modified based on that determination.
The determination may include comparing the coding scheme indicator of the received data packet to a coding scheme command. It may also include determining whether a received data packet is a null data packet. Based on that determination, the modification of the coding scheme may comprise altering the coding scheme command when the mobile station is adaptable.
A subsequent packet uplink acknowledgement including an altered coding scheme command may be sent when the mobile station is adaptable. Or, a subsequent packet uplink acknowledgement including an unaltered coding scheme command may be sent when the mobile station is not adaptable. Or, a subsequent packet uplink acknowledgement including an unaltered coding scheme command may be sent when the received data packet is a null data packet.
A coding scheme adaptation flag associated with the mobile station may be set and the coding scheme may be modified based on the coding scheme adaptation flag. A value of a coding performance parameter may be determined and the coding scheme may be modified based on the value of the coding performance parameter. Another aspect of the invention includes a computer usable medium with a program for determining coding scheme adaptation capability of a mobile station.
The aforementioned, and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.